Copper base alloy



' Aug. 6, 1940. M LLY 2.210573 COPPER BASE ALLOY Filed March 16, 1940fiyt'fly 77/772 /7 Hour s WITNESSES: INVENTOR Patented Aug. 6,1940

UNITED STATES corrmt BASE ALLOY James M. Kelly, Traiford, Pat, assignorto Westinghouse Electric & Manufacturing Company, East Pittsburgh, Pa.,a corporation of Pennsylvania Application March 16, 1940, Serial No.324,435

4 Claims. (01. 75159) This invention relates to copper base alloys andin particular, to copper base alloys of the aluminum bronze type.

Alloys of aluminum and copper are known in the industry and are employedwhere the characteristics of corrosion resistance is required. The knowncopper aluminum alloys are, however, limited to certain applicationswhich do not require high physical strength and hardness.

It is an object of this invention to provide a copper base alloy of thealuminum bronze type which will have high physical strength, togetherwith corrosion resistant characteristics.

Another object of this invention is to provide a copper base alloy ofthe aluminum bronze alpha type which may be precipitation hardened toimpart high physical strength thereto, the resulting alloy beingresistant to corrosion.

Other objects of this invention will become apparent from the followingdescription when taken in conjunction with the accompanying drawing, thesingle figure of which is a graph, the curves of which illustrate thehardness values obtained with representative alloys of this invention.

The alloys of this invention are prepared in accordance with standardmelting practice from copper, aluminum, cobalt and iron. Sufiicientaluminum is employed to give an aluminum content of from 5% to 7% whileeach of the cobalt and iron contents in the copper base ranges from .5%to 5%. These alloying elements cooperate to give an aluminumbronze-alloy of the alpha type which is resistant to oxidation and whichcan be heat treated to impart a high strength to the alloy whereby thealloy is satisfactory for use as a casting alloy.

In order to develop the mechanical strengthv of the alloy, castingstherefrom are subjected to a precipitation hardening treatmentcomprising subjecting the alloy to a high temperature below the meltingpoint of the alloy for obtaining a high solid solution of the cobalt andiron in the alloy, quenching the alloy' from the high temperature toretain the cobalt and iron in solid solution and then reheating orageing the alloy at a lower or ageing temperature for a period of timesufilcient to precipitate the cobalt or certain of the cobalt compoundsformed therein and the iron from the solid solution state. In practice,heating the alloy at a temperature between 750 C. and 1025 C. is foundto effect a high solid solution of the cobalt and iron in copper whilereheating or ageing the alloy at a temperature of between 350 C. and 650C. effects the precipitation of the cobalt or cobalt compounds and ironto impart the desired characteristics to the resulting alloy.

As a specific example of the improved hardness characteristic obtainedwith the alloy of this invention, reference may be had to theaccompanying drawing, the curves of which represent the values obtainedfor different representative alloys illustrating this invention. In thedrawing, the abscissa represents the ageing time in hours and theordinate represents the Rockwell B hardness values obtained. The curvesof the drawing are based onhardness values obtained on' the five alloysof the following table, the aluminum alloying content of these alloysbeing maintained a constant in order to better illustrate the beneficialeffects of the cobalt and iron as alloying elements in alpha bronzes ofthe copper aluminum type.

Composition Alloy No.

Percent Percent Percent Percent 00 Fe Al Cu In the drawing, curves 0, I,2, 3 and 5 represent results obtained with the alloys in the order givenin the table and containing 0, 1, 2, 3 and 5% respectively of each ofiron and cobalt after they were subjected to a heat treatment consistingof quenching them from a temperature of 950 C.

and ageing them at a temperature of 500 C. for

different periods of time./ From these curves, it is quite apparent thatthe iron and cobalt cooperate with each other and with the aluminum inthe copper base to give an alloy of improved characteristics. This isquite apparent from a comparison of curves I, 2, 3 and 5 which representthe results obtained with alloys of this invention with the resultsshown by curve 0 which represents the results obtained with a binarycopper aluminum alloy having the same aluminum content.

The alloys of this invention have very good thermal endurancecharacteristics, that is, the characteristic to retain hardness orstrength at elevated temperatures. These copper-cobaltiron-aluminumalloys have been found to retain their high strength even when subjectedto temperatures of 850 C.- for periods of time of hours.

Since the copper base alloys containing the aluminum, cobalt and ironwithin the ranges given are suitable for casting and can beprecipitation hardened to impart strength thereto, they can be used inmaking articles where casting to a predetermined shape is a prerequisiteand where high strength castings are required. It also has been foundthat cold work can be applied to the heat treated alloys of thisinvention to further improve their strength. As illustrative of the hightensile strength obtained with alloys of this invention both in the heattreated cast condition and also in the heat treated and cold workedcondition, reference may be had to the following table in which theresults'obtained with the alloys identified in the table givenhereinbefore are listed.

. Tensile strength pounds per square inch Alloy No.

Treatment Treatment 31, 400 48, 000 000 000 its. $3000 98, 000 120, 00084, 200 90, 000

In obtaining the results listed in the foregoing table, each of thealloys was subjected to each of two treatments, Treatment A consistingof quenching the alloy from a temperature of NW C. and ageing it for 20hours at a temperature of 500 C. while Treatment B is a similar heattreatment with the addition of supplementary cold work in the amount ofa 25% reduction in area of the article worked. Thus the alloys of thisinvention, due to the cooperation of the cobalt and iron, have all theadvantages of the alpha type binary alloys with the addition that theyare susceptible to precipitation hardening heat treatment.

The alloys of this invention containing from 5% to 7% of aluminum andfrom .5% to 5% of each of cobalt and iron, with the balance oopper, alsohave the desirable characteristic of being resistant to oxidation whensubjected to heat at elevated temperatures. In order that the alloy mayhave oxidation resistant characteristics it is preferred that thealuminum content be not less than 5%. As a. specific example of theoxidation resistant characteristic alloys of this invention, it is foundthat articles formed therefrom are entirely free from any evidence ofoxide formation thereon even after being exposed in circulating air at atemperature of 850 C. for a period of time of hours.

From the foregoing it is quite apparent that a copper base alloycontaining aluminum, iron and cobalt within the ranges given is producedwhich is entirely satisfactory as a casting alloy since the alloyingelements cooperate when subjected to precipitation hardening to imparthigh strength thereto. The alloy having the composition of 2% iron, 7%aluminum, 2% cobalt and 89% copper is quite satisfactory, since theresults obtained therewith approximate the results obtained with themaximum alloying contents. All the alloys containing the alloyingelement within the ranges given are resistant to oxidation and becauseof their high strength will find many and varied applications where suchcharacteristics are necessary.

Although this invention has been described with reference to aparticular embodiment there-' of, it is, of course, not to be limitedthereto except insofar as is necessitated by the description thereof andthe scope of the appended claims.

I claim as my invention:

1. An alloy comprising from 5% to 7% of aluminum. from .5% to 5% ofiron, from .5% to 5% of cobalt, and the balance substantially allcopperl 2. An alloy comprising from 5% to 7% of aluminum, from 2% to 5%of iron, from 2% to 5% of cobalt, and the balance substantially allcopper.

3. As an article of manufacture, an alloy comprising from 5% to 7% ofaluminum, from .5% to 5% of iron, from .5% to 5% of cobalt, and thebalance substantially all copper, cast to a predetermined shape andprecipitation hardened to give it high physical shape, said articlebeing resistant to oxidation at temperatures of up to between 750 C. and850 C.

4. An alloy composed of about 7% of aluminum, about 2% of cobalt, about2% of iron and the balance copper.

JAMES M. KELLY.

